Horowitz C J, Caballero O L, Berry D K
Department of Physics and Nuclear Theory Center, Indiana University, Bloomington, Indiana 47405, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Feb;79(2 Pt 2):026103. doi: 10.1103/PhysRevE.79.026103. Epub 2009 Feb 3.
Recently, crust cooling times have been measured for neutron stars after extended outbursts. These observations are very sensitive to the thermal conductivity kappa of the crust and strongly suggest that kappa is large. We perform molecular dynamics simulations of the structure of the crust of an accreting neutron star using a complex composition that includes many impurities. The composition comes from simulations of rapid proton capture nucleosynthesis followed by electron captures. We find that the thermal conductivity is reduced by impurity scattering. In addition, we find phase separation. Some impurities with low atomic number Z are concentrated in a subregion of the simulation volume. For our composition, the solid crust must separate into regions of different compositions. This could lead to an asymmetric star with a quadrupole deformation. Observations of crust cooling can constrain impurity concentrations.
最近，人们已经测量了中子星在长时间爆发后的外壳冷却时间。这些观测结果对地壳的热导率κ非常敏感，并强烈表明κ很大。我们使用包含许多杂质的复杂成分，对吸积中子星外壳的结构进行了分子动力学模拟。该成分来自于快速质子俘获核合成随后电子俘获的模拟。我们发现热导率因杂质散射而降低。此外，我们发现了相分离。一些低原子序数Z的杂质集中在模拟体积的一个子区域中。对于我们的成分，固态地壳必须分离成不同成分的区域。这可能导致一颗具有四极变形的不对称恒星。对地壳冷却的观测可以限制杂质浓度。
